A couple of months ago, it was reported that cross-platform multiplayer interaction for Team Fortress 2 was achieved at Valve's offices and the developer confirmed that interplay between the PC and Xbox 360 version of the game was "technically done."
Unfortunately, Valve's Doug Lombardi, who revealed that such a cross-platform multiplayer between PC and Xbox 360 was possible, has now confirmed that it won't make it into the final game.